By default, after showing the first GTK2.Window for each GDK2.Screen,
GTK+ calls GDK2.Screen->notify_startup_complete(). Call this function to
disable the automatic startup notification. You might do this if your
first window is a splash screen, and you want to delay notification until
after your real main window has been shown, for example.
In that example, you would disable startup notification temporarily,
show your splash screen, then re-enable it so that showing the main
window would automatically result in notification.
GTK2.root_window()